Question

A cliff swallow nest is 86 meters above a canyon floor.
The elevation of the nest is −56 meters. What is the elevation of the canyon
floor?

Answer 1

Elevation in this case is a measure of how high a location is relative to sea level.

It's a good idea to draw a vertical line to model this problem, and then put a tick mark on the middle of the line to represent an elevation of 0 ( sea level).

Now put a tick mark at the nest's elevation: -56 m. This number is lower than 0, so this tick mark should be somewhere below the first tick mark.

Now time to think: the nest itself is at -56 m elevation, yet it is 86 m above the canyon floor, or in other words, the canyon floor is 86 m below the nest. Place the tick mark for the canyon floor even further down the line.

I will leave it to you to now work out how far the canyon floor tick is below the sea level tick.